Matt Cassel agreed to terms on a two-year deal with the Vikings on Thursday afternoon, just hours after his long-expected release from Kansas City, NFL sources said.

ESPN's Adam Schefter reported Cassel will compete for the starting job. But two sources with knowledge of the situation insist he's strictly being brought in as a backup to Christian Ponder.

Cassel, 30, spent the past four seasons with the Chiefs. He had two years left on the $63 million megadeal he signed shortly after being acquired from New England in 2009.

His release had been inevitable since the Chiefs signed Chase Daniel to a three-year, $10 million contract on Tuesday to backup newly acquired starter Alex Smith -- the latest sign of a robust market for No. 2 quarterbacks.

Last week, Miami re-signed Matt Moore a two-year, $8 million extension last week. On Wednesday, Arizona gave Drew Stanton three years and $8.2 million, with $12 million in escalators if he ends up starting.

Terms were not immediately available on Cassel's deal, although it figures to fall in that $3 million annual range, contrary to reports he could make $4 million a year. CBSSports.com reported Cassel can void the deal after the 2013 season.

An NFL source told 1500ESPN.com earlier in the day Cassel was the Vikings' man, if they could agree to contract terms. Fox's Jay Glazer first reported the deal is done.

Vikings coach Leslie Frazier and general manager Rick Spielman have said repeatedly Ponder won't face competition for the starting job. But it was clear for months they wanted to upgrade from Joe Webb as a backup plan.

The only other quarterback under contract is McLeod Bethel-Thompson, who hasn't appeared in a regular-season NFL game.